Heterochromatin analysis in the fish species Liposarcus anisitsi (Siluriformes) and Leporinus elongatus (CHARACIFORMES)

The chromosomes of two neotropical freshwater fish species, namely Liposarc us anisitsi (Siluriformes, Loricariidae) and Leporinus elongatus (Characifo rmes, Anostomidae), were investigated by means of C-banding, Ag-NORs, fluor ochrome staining and banding by hot saline solution (HSS) treatment, to rev eal patterns of heterochromatin differentiation. The karyotype of L. anisit si is described for the first time. Staining with the CC-specific fluoresce nt antibiotic mithramycin (MM) revealed bright signals in some C-banded blo cks in both species, suggesting that these MM+ heterochromatin contains GC- rich DNA. Banding by denaturation employing HSS, followed by Giemsa stainin g, yielded corresponding results documenting the thermal stability of CC-ri ch DNA part of heterochromatin positive after C-banding. In L. elongatus th e Ag-NOR also followed the above banding patterns. However, in L. anisitsi the Ag-NOR was MM+ but negatively stained after C-banding and HSS treatment . L. elongatus also showed C-banded segments that were negative for mithram ycin staining and HSS treatment. The results obtained evidence the heteroch romatin heterogeneity in these fish species.